Beat oscillator



May 5, 1942.

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E. OLSON 2,281,709

BEAT OSCILLATOR "Filed Feb. 17, 1941 [g 7 V IIIII I I INVENTOR. ELMEE'[15cm Patented May 5, 1942 UNITED STATES PATENT OFFICE BEAT OSCILLATORElmer Olson, Pomeroy, Iowa Application February 17, 1941, Serial No.379,219

1 Claim.

The principal object of this invention is to provide a tuned grid beatoscillator for accurately calibrating radio sets or other tunedelectrical apparatuses.

A further object of this invention is to provide a beat oscillatorcircuit which will radiate a tuned frequency beat on any pre-selectedfrequency for setting or locating station frequencies and for adjustingtrimmer condensers, push button tuning controls or the like of a radioset.

A still further object of this invention is to provide an oscillator ofthe tuned grid 'type which can be set at a desired frequency and whichwill, when a radio set is tuned to the principal harmonic of thefrequency, give a visual signal to indicate the resonance of therespective circuits relative to each other.

A still further object of this invention is to provide a beat oscillatorcircuit which is extremely economical in manufacture, durable andefiicient in use.

These and other objects will be apparent to those skilled in the art.

My invention consists in the construction, arrangement and combinationof the various parts of the device, whereby the objects contemplated areattained as hereinafter more fully set forth, pointed out in my claimand illustrated in the accompanying drawing, in which:

The figure is a diagrammatic view of the circuit employed in my beatoscillator or frequency meter.

It has heretofore been difficult to set the push buttons of a radiounless the actual broadcasting station to be selected is tuned in, andeven then it is difficult to hit the period of resonance of the carrierwave that is in exact tune with the station. Some attempts have beenmade to do this by the use of an ordinary wave meter, but this isdifficult due to the broadness of the carrier of such mechanisms and thefact that the wave meter must have its antenna pick-up changed for eachfrequency variation. Furthermore, such frequency beat meters relied uponan audible signal rather than a visual indicator, were extremelycritical as to their own inherent adjustment. I have overcome suchdisadvantages as will be appreciated and as will be hereinafter morefully set forth.

I have used the numeral l to indicate an ordinary triode type of vacuumtube having the ordinary plate element ll, grid l2 and filament [3. Oneside of the filament element is connected to the center tap of a batteryor like M,

outer lead wires of the battery M. Imposed in this last mentioned leadline is a switch l5 and rheostat It. The other end of the battery I4 isconnected through the medium of an electric lead line ll with one sideof a milliammeter Ill. The numeral l9 indicates the primary windings ofa coil having one end in electrical communication With the plate II andits other end in communication through a lead line 20 with the otherside of the milliammeter H3. The numeral 2| indicates a condenser placedin multiple or shunted across the two terminals of the milliammeter lt.The secondary winding of the coil I have designated by the numeral 22,which is shunted by a variable condenser 23 as shown in the drawing. Theupper end of this coil 22 is connected to one side of a condenser unit24 and the other side of the condenser 24 is connected, through themedium of an electric lead line 25, with the grid l2 of the tube Ill.The lower end of the coil 22 is connected to the central tap of thebattery I. The antenna plate 26 is connected into the circuit includingthe grid 12, variable condenser 23, and coil 22 as appears clearly inthe drawing. The numeral 21 indicates an electric lead line having oneof its ends in electrical communication with the lead line 25 and itsother end designed to be secured to the control grid of a radio or like.

The practical operation of my device is as follows:

The complete unit is placed at a distance from the radio set to be tunedand the filament switch I5 is closed, thereby activating the filament l3of the vacuum tube ill. The variable condenser is tuned to the frequencydesired and calibrated for that frequency. This causes the vacuum tubeI0 to oscillate at a certain frequency, thereby registering a definitebeat on the milliammeter I8. The radio set is then tuned until thehighest frequency of beat is indicated by the milliammeter, at whichtime the radio receiving set will be in resonance with the frequencydetermined on the condenser unit 23. Inasmuch as all of the variousfrequencies can be calibrated on the control shaft or dial of thecondenser 23, it is merely necessary to set this condenser at anydesired frequency such as one thousand kilocycles, twelve hundredkilocycles or the like, and then tune the radio receiving apparatusesuntil the highest frequency of beat is noted on the milliammeter IS. Theset can then be adjusted and will be accurately in tune for thefrequency so determined. In some instances, it is necessary and theother side is connected to one of the to connect the wire 21 to acontrol grid of the controls thereon.

radio set in order to intensify the reading of the milliammeter and thefrequency of its beat. Thus it is possible to trace the operation of theradio set over its entire frequency band to determine the correctcalibration point on the radio set for pre-setting automatic pushbuttons or other Thus it will be seen that I have provided a beatoscillator for use in tuning radio receiving apparatuses which fulfillsall of my objects and presents many more obvious advantages. Its extremesimplicity of operation makes it a highly desirable instrument for usein setting automatic push button controls on across said secondary ofsaid tuning grid, a milmodern radio apparatuses, and the equipment canbe made in a small compact form and gives a visual signal indicating theperiod of resonance of the receiver relative to the frequency set'on mydevice.

Some changes may be made in the construction and arrangement of myimproved beat oscillator without departing from the real spirit and.purliammeter having one of its terminals in communication with a sourceof electrical energy and its other side in communication with theprimary winding of said tuning grid, and an electric lead line incommunication with the other'side of said primary coil and the plate ofsaid tube.

' ELMER OLSON.

